Merge lp:~gnuoy/charm-helpers/current-dc-leader into lp:charm-helpers

[Liam Young]

[Liam Young (gnuoy)]

This mp implements freyes suggestion of using pacemaker Designated Controller as a way to determine leadership. See https://bugs.launchpad.net/charms/+source/percona-cluster/+bug/1452365/comments/9

[lp:~gnuoy/charm-helpers/current-dc-leader]

375. By Liam Young on 2015-05-15

Use constant for DC resource string and add doc string

[James Page (james-page)]

Minor niggle - please fix and merge!

review: Approve

[lp:~gnuoy/charm-helpers/current-dc-leader]

376. By Liam Young on 2015-05-15

Fix unit test for is_crm_leader to use DC_RESOURCE_NAME

[Adam Collard (adam-collard)]

review: Needs Fixing

=== modified file 'charmhelpers/contrib/hahelpers/cluster.py'
--- charmhelpers/contrib/hahelpers/cluster.py	2015-02-16 14:26:57 +0000
+++ charmhelpers/contrib/hahelpers/cluster.py	2015-05-15 09:18:20 +0000
@@ -52,6 +52,8 @@
     bool_from_string,
 )
 
+DC_RESOURCE_NAME = 'DC'
+
 
 class HAIncompleteConfig(Exception):
     pass
@@ -95,6 +97,27 @@
     return False
 
 
+def is_crm_dc():
+    """
+    Determine leadership by querying the pacemaker Designated Controller
+    """
+    cmd = ['crm', 'status']
+    try:
+        status = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
+        if not isinstance(status, six.text_type):
+            status = six.text_type(status, "utf-8")
+    except subprocess.CalledProcessError:
+        status = None
+    current_dc = ''
+    for line in status.split('\n'):
+        if line.startswith('Current DC'):
+            # Current DC: juju-lytrusty-machine-2 (168108163) - partition with quorum
+            current_dc = line.split(':')[1].split()[0]
+    if current_dc == get_unit_hostname():
+        return True
+    return False
+
+
 @retry_on_exception(5, base_delay=2, exc_type=CRMResourceNotFound)
 def is_crm_leader(resource, retry=False):
     """
@@ -104,6 +127,8 @@
     We allow this operation to be retried to avoid the possibility of getting a
     false negative. See LP #1396246 for more info.
     """
+    if resource == DC_RESOURCE_NAME:
+        return is_crm_dc()
     cmd = ['crm', 'resource', 'show', resource]
     try:
         status = subprocess.check_output(cmd, stderr=subprocess.STDOUT)

=== modified file 'tests/contrib/hahelpers/test_cluster_utils.py'
--- tests/contrib/hahelpers/test_cluster_utils.py	2015-01-06 15:28:29 +0000
+++ tests/contrib/hahelpers/test_cluster_utils.py	2015-05-15 09:18:20 +0000
@@ -6,6 +6,24 @@
 
 import charmhelpers.contrib.hahelpers.cluster as cluster_utils
 
+CRM_STATUS = b'''
+Last updated: Thu May 14 14:46:35 2015
+Last change: Thu May 14 14:43:51 2015 via crmd on juju-trusty-machine-1
+Stack: corosync
+Current DC: juju-trusty-machine-2 (168108171) - partition with quorum
+Version: 1.1.10-42f2063
+3 Nodes configured
+4 Resources configured
+
+
+Online: [ juju-trusty-machine-1 juju-trusty-machine-2 juju-trusty-machine-3 ]
+
+ Resource Group: grp_percona_cluster
+      res_mysql_vip      (ocf::heartbeat:IPaddr2):       Started juju-trusty-machine-1
+       Clone Set: cl_mysql_monitor [res_mysql_monitor]
+            Started: [ juju-trusty-machine-1 juju-trusty-machine-2 juju-trusty-machine-3 ]
+'''
+
 
 class ClusterUtilsTests(TestCase):
     def setUp(self):
@@ -41,6 +59,20 @@
         self.assertFalse(cluster_utils.is_clustered())
 
     @patch('subprocess.check_output')
+    def test_is_crm_dc(self, check_output):
+        '''It determines its unit is leader'''
+        self.get_unit_hostname.return_value = 'juju-trusty-machine-2'
+        check_output.return_value = CRM_STATUS
+        self.assertTrue(cluster_utils.is_crm_dc())
+
+    @patch('subprocess.check_output')
+    def test_is_crm_dc_false(self, check_output):
+        '''It determines its unit is leader'''
+        self.get_unit_hostname.return_value = 'juju-trusty-machine-1'
+        check_output.return_value = CRM_STATUS
+        self.assertFalse(cluster_utils.is_crm_dc())
+
+    @patch('subprocess.check_output')
     def test_is_crm_leader(self, check_output):
         '''It determines its unit is leader'''
         self.get_unit_hostname.return_value = 'node1'
@@ -79,6 +111,12 @@
         self.assertFalse(cluster_utils.is_crm_leader('vip'))
         self.assertFalse(mock_time.called)
 
+    @patch.object(cluster_utils, 'is_crm_dc')
+    def test_is_crm_leader_dc_resource(self, _is_crm_dc):
+        '''Call out to is_crm_dc'''
+        cluster_utils.is_crm_leader(cluster_utils.DC_RESOURCE_NAME)
+        _is_crm_dc.assert_called_with()
+
     def test_peer_units(self):
         '''It lists all peer units for cluster relation'''
         peers = ['peer_node/1', 'peer_node/2']